1. Field of the Invention
The invention relates to a central tube fiber optic cable having a bundle support member for supporting optical fibers therein.
2. Background
There are generally two basic types of optical fiber cables including a Central Tube Cable and a Loose Tube Cable. A Loose Tube Cable includes a central strength member around which buffer tubes, housing the fibers, are wound. A jacket is provided around the buffer tubes. A Central Tube Cable does not have a central strength member in the optical fiber cavity. Instead, a Central Tube Cable generally includes a pair of radial strength members that are embedded in the cable jacket at positions diametrically opposite one another. The central cavity defined by the jacket, without any strength member, may include bare fibers, ribbons or buffer tubes containing optical fibers.
The problem with the Central Tube Cable design with buffer tubes is that, other than friction between the buffer tubes and the inner surface of the jacket, there is nothing to prevent the buffer tubes from moving along the longitudinal axis of the cable. In aerial applications, these Central Tube Cables are installed between telephone poles, normally using a lashing method, on a steel messenger. At the end of the cable segment, the cable is connected to a splice box in which the fibers of one cable are spliced with the fibers of another cable. In order to support the cable, the radial strength members, that are embedded in the cable jacket, are fixedly secured to the splice box.
When the cable is subjected to a significant load (due to sag, wind, ice build-up or the like) the buffer tubes and fibers are also subjected to a strain. Since the buffer tubes and fibers are not restrained against axial movement, the strain resulting from the load may cause the buffer tubes and associated fibers to be pulled out of the splice box detrimentally affecting the optical performance of the fibers.